DarkStar66

I was trying to explain what a turbo does the other day and thought 'Why have a complicated turbo instead of a larger capacity NA engine?'.

As far as I understand, the turbo compresses the air/fuel mixture going into the cylinders so that you get more bang from the ignition. Thus a 2 litre engine gets as much power as a 3 litre engine, depending on the pressure that the turbo provides.

So why not have a 3 litre engine in the first place? It probably means you'll need 6 cylinders instead of 4 but is a turbo and intercooler less complicated? Also, you won't get any lag.

Can anyone explain the point of going the turbo route?

Marc

Tidgy

true, but, if you increase from 4 to 8 pistons your are almost doubling the material and therefore weight of the block (ok bit of a basic description but you get the idea), and also increasing size of the engine. turboing uses same block but gets more out of it.

BlueSimon

To me its down to efficiancy, you cant have any fuel/air mix with petrol unlike diesel it has to be kept within a ratio, therfore bigger engine = more fuel required regardless of power output, small engine with turbo, much greater range of fueling.

Simon

ALi-B

iTrader: (1)

Depends how you look at it. But basically it lie down to cost for the manufacturers to implement it in the proposed vehicle.

A 6pot engine is heavier, and has more moving components. It also take up more space. This needs to be considered with crumple zones and weight distribution too.

A turbo is a cheap, quick, simple and a somewhat crude way of boosting an engine's performance without creating any large space or weight issues. And only minimal design changes are needed to convert a N/A engine (i.e Normal aspriated EJ20 ) to a turbo. That being lower the compression ratio and use stronger the rods and pistons etc (if needed). Saving the need to retool and cast a new engine block and cylinder heads.

The disadvantages are obvious - you can't beat CC. You have lag and an engine with "peaky" performance and a torque band that spike mid revs. Cooling issues, stress and load issues of producing more BHP per cylinder. And of course emissions and fuel efficiency (lower compression and poor off-boost breathing). Many tricks are used to get round this such as low pressure turbos, which retain high compression and use small turbos to avoid lag and avoid peakyness and mid rev-surge (i.e VW). Intercoolers and oil coolers to help heat dissapation and engine managment to accurately control boost, fuel and ignition timing.

Diesel engines, on the otherhand is a different story. A deisel engine runs infintely lean, and thus needs as much air pumped in to obtain decent power. So for a diesel engine to perform, forced induction is the only option. This gives much less negative issues than with petrol engines that are turbocharged.

Neilo

you coudl look at it another way....NA = permenant lag

alloy

Turbos are only there so you can put a dumpvalve on your car

RB5_245

Turbos are a lot simpler that these new complicated high output/litre engines, otherwise you go down the american route of massive engine, high weight and (relatively) low power.

Ie and MY05 spec C, 2.0l makes about 320bhp, a chevy small block ie holden 5.7 makes about 340. though i think the latest corvettes and the like were up to around 400, it's still rubbish bhp/litre

robsw

Supercharged engines are the way to go, basically a belt driven turbo, but without lag.

scoobfan

But far more expensive and more strain on engine components.

For absolute ***** out power you cannot beat a Turbo driven car

Rob

robsw

Do not agree, Rob, for absolute ***** out power you cannot beat a 500ci V8, massive carbs (not efi), and a supercharger.

The beauty of a turbo is you get something for nothing, you just have to get around the lag situation as best as is possible.

Robin.

New_scooby_04

iTrader: (4)

*Coughs* Fuel consumption!

Ns04

[Davey]

Yes you can, you stick 4 turbos on the V8 and its even more powerful

Because the turbo is using a wasted resource (exhaust) you cant really beat them for efficient power.

Superchargers sap up loads of power, yes they have no lag but they are not as efficient as a turbo.

scoobfan

But it will handle like a bag of piggin dog poo, like all yank cars do !

You can't brake as late due to massive amounts of nose dive because
of the massive amount of weight.

If your going to run a large block car, the engine should be at the back,
like F1

Sorry, I do respect your views, but your wrong !!!!!

Rob

scoobfan

You get it don't ya Davey !!

Rob

robsw

Sorry I am only talking in terms of air induction, as this is the hard factor to achieve in combustion engines. It is easy to horse fuel in to achieve the correct ratio, just harder to get the air there in the first place.

If you want more performance you expect to use more fuel, using a turbo or supercharger, otherwise we would all stick with a normally aspirated engine (unless you go the diesel route of course), for better fuel economy.

Rob.

NotoriousREV

Doesn't the McMerc sap around 150bhp just to drive the SC? That's a serious amount of power loss that you just wouldn't get with a turbo.

The boost a supercharger makes is also a linear relationship with engine speed, a turbo isn't (hence the massive mid-range a turbo can produce).

New_scooby_04

iTrader: (4)

I know mate, it's just when you said "something for nothing" as a Scooby driver -and by now a part shareholder in Shell - I just couldn't resist!!!

robsw

You mentioned ***** out power, not relating to a particular vehicle or if it can go around corners or not. So I was thinking along these lines:

http://www.santapod.co.uk/dr_classes.php

I don't think the top fuel cars run several turbo's just one rather large supercharger. There are no other cars with internal combustion engines that accelerate quicker.

If you are talking ***** out power and driveability, then yes I agree with what you are saying.

Rob.

scoobfan

There is only one benefit from driving a supercharged car and that is...

The noise, spine chilling !!!!

Remember the Maclaren Mercedes SLR on Topgear, it sounded like a
spitfire at full chat, OOOOH
Rob

robsw

That's ok, no probs NS04!

Rob.

scoobfan

[quote=robsw]Supercharged engines are the way to go, basically a belt driven turbo, but without lag.[/quote

You wrote this, we don't all drive Nitro Methane cars on the road now do we
We have to go around corners at some point.

Rob

robsw

Absolutely incredible, and if you havn't heard a top fuel dragster then you must, the 1st time I heard one I was in disbelief!

The 'main event' at santa pod is coming up end of May, that is where you will experiance the best display of top fuel vehicles in the UK, and the odd jet engined vehicle too.

I'm addicted anyway as you may be able to tell!

Rob.

robsw

[quote=scoobfan]

Quote:

Originally Posted by robsw

Supercharged engines are the way to go, basically a belt driven turbo, but without lag.[/quote

I think you would definately have the odd funny look if you took one up the highstreet!

Rob.

scoobfan

Quite a trip for you too make from Bristol !! and I totally agree, they are
awsome.

I have seen the Fireforce 2 twice now and it never ceases to amaze me,
I become like a small child, all gigally and smiley after the run, such a rush
Take a look here for the latest on the Drag scene.

www.ukdrag-racing.co.uk

Rob

ALi-B

iTrader: (1)

<Cough> http://superchevy.com/technical/engi...09sc_assembly/

And it's cheaper to buy as a complete turn key engine than a turn key scooby engine...just need something to put it in

Lighter than a Rover V8 but 7.0 instead of 3.5litres and the torque never drops below 350lb/ft from 1000-7000rpm (470lb/ft peak), basic design but using the lastest materials and manufactureing and can still match your rice rocket for appauling fuel consumption (alledged to be between 18mpg to as good as 28mpg) And it's STOCK...tweek it or supercharge it and it's going to be a stormer!!

53

iTrader: (41)

2.0ltr turbo production car has something to do with the rally qualifications ? I think.

robsw

I'll check the link Rob, thanks. Fireforce 2 also has the same effect on me. But the top fuel dragsters are really abusing nature, absolutely incredible.

We used to go to the shakespere county track, but it's just not as good as santa pod, with few top fuellers, so we usually camp the whole 4 day event at the end of may, and again at the start of September at pod for the finals (depending on the weather).

Rob.

scoobfan

Match it, you mean double it !!

And what would it be like in the twisties ??

Rob

RB5_245

scoobfan

Nice edit !!

Rob